Both Intel FMA and AMD SSE5 support FMA. For -mfma, which enables
Intel FMA and is a dummy at the moment, or -msse5, we will
generate FMA instructions for
double f;
void
foo (double x, double y, double z)
{
f = x * y + z;
}
What FMA should "-mfma -msse5" generate? Also currently, with
"-O2 -mavx -msse5", we generate
foo:
fmaddsd %xmm2, %xmm1, %xmm0, %xmm0
vmovsd %xmm0, f(%rip)
ret
which won't run on any machines. For "-mfma -msse5" and
"-mavx -msse5",
1. Should these combinations be allowed? If allowed,
2. Should the last option turn off the first one?
--
Summary: -mfma/-mavx and -msse5/-msse4a don't work together
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hjl dot tools at gmail dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38201
